Recently, in accordance with miniaturization of a circuit pattern of a semiconductor device, a pattern size guarantee for a mask material such as a photo mask has been more important than ever.
Conventionally, the pattern size guarantee has been carried out by a method of drawing a drawing pattern to a mask substrate so as to form a photo mask and then deciding whether an average value and a variation amount of the pattern sizes measured at respective measuring points on the photo mask satisfy a predetermined pattern measurement specification or not. This method is, for example, disclosed in JP-A-2003-241364.
However, conventional mask size guarantee methods have disadvantages that a measurement time would be lengthened if the measurement points are set over the whole pattern in order to improve accuracy of the mask size guarantee.